In 1995 William Louis and colleagues at Los Alamos National Laboratory reported the first evidence of neutrino flavor oscillation in an accelerator experiment. The report was disquieting, and became more so over the next three years as its statistical significance was bolstered by more data from the LANL experiment.
Why the disquiet? After all, neutrino oscillation, the metamorphosis of neutrino flavors with a probability that oscillates with travel distance L like sin2(L/λ), was already well attested for neutrinos from the Sun and from cosmic-ray showers in the atmosphere. The characteristic oscillation length λ is given by 4ħE/c 3Δm 2, where E is the neutrino’s energy and Δm 2 is the difference between the squared masses of the two neutrino mass eigenstates involved.
The prevailing model of neutrino oscillation assumes that there are three different neutrino mass eigenstates in nature...
